This invention relates to a recording and/or reproducing apparatus for a 5.25-inch large-capacity magnetooptical-disk.
The conventional 5.25-inch magnetooptical-disk recording and/or reproducing apparatus drives a magnetooptical-disk of 325 MB/side, which is standardized by ISO/IEC 10089, to rotate it at 2400 rpm, and records or reproduces information on or from each side of the disk. In this case, the data transfer rate is 920 KB/s. In addition, the interface to the host interface is SCSI-1, and the apparatus size is the same as the 5.25-inch magnetic disk recording and/or reproducing apparatus of full height (140 mm.times.208 mm.times.82.6 mm).
The bias magnetic field generator of the magnetooptical-disk recording and/or reproducing apparatus, upon recording, applies a vertical magnetic field to the recording medium in one direction, and upon erasing, applies the field to it in the other direction, or opposite direction. This magnetic field, in cooperation with the action of the very small light spot formed on the recording medium through an object lens, acts to erase data from or record data on the recording medium. The bias magnetic field generator is of the electromagnet coil type or of the permanent magnet type.
The conventional bias magnetic field generator of the electromagnet coil or permanent magnet type is so provided that the light spot can be formed along the center line of the bias magnetic field generator on the recording medium. An example of the provision of an electromagnet coil on the opposite side of the recording medium to the object lens is described in JP-A-59-203258. An example of the provision of an electromagnet on the object-lens side of the recording medium is described in JP-A-57-27449. On the other hand, an example of the provision of a permanent magnet on the opposite side of the recording medium to the object lens is described in JP-A-57-24047. However, there is no idea that the permanent magnet is disposed on the object-lens side of the recording medium.